The present invention relates to an inkjet printhead having a plurality of pressure chambers each of which is fluidly connected on the one hand, via an ink supply path, to a common ink reservoir and on the other hand to a nozzle, wherein an actuator is provided for each pressure chamber for pressurizing the ink contained therein, so as to eject an ink droplet through the nozzle in response to a print signal.
EP-A-1 022 140 describes a drop-on-demand inkjet printhead of the type indicated above, wherein the nozzles are arranged in two parallel linear arrays, so that a plurality of pixel lines of an image can be printed simultaneously. The pressure chambers associated with the nozzles of both arrays are configured as elongated ink channels that are formed in opposite surfaces of a common substrate and extend in parallel to one another. The downstream ends of the ink channels each converge into an associated nozzle, whereas the upstream ends of the ink channels of both arrays are connected to the common ink reservoir through their respective ink supply paths. The actuators are formed by piezoelectric elements that are arranged along each ink channel. When an ink droplet is to be expelled from a specific nozzle, the associated actuator is energized such that the piezoelectric element will first contract, so that ink is sucked-in through the ink supply path, and the piezoelectric element will then expend again, so that the liquid ink contained in the ink channel is pressurized and an acoustic pressure wave will propagate towards the nozzle.
A problem encountered with printheads of this type is the occurrence of cross-talk among the various nozzles. A major reason for this cross-talk phenomenon is the propagation of acoustic waves in the solid material of the piezoelectric actuators and in the common substrate in which the ink channels are formed. As is known in the art, this kind of cross-talk can be suppressed, for example, by selecting an appropriate design for the substrate and the ink channels and by providing a suitable support structure for the piezoelectric actuators.
Another source of cross-talk may be the propagation of acoustic waves through the liquid ink in the ink supply system. In order to avoid cross-talk of this kind, EP-A-0 726 151 proposes a printhead in which the ink supply paths connecting the pressure chambers to the common ink reservoir comprise acoustically matched sets of inlet filters, inlet ports, and inlet channels, which are designed to avoid, through acoustic matching, the propagation of acoustic waves from the various pressure chambers into the ink reservoir. In the printhead described in this document, the ink reservoir is formed by a closed chamber which is bounded on one side by a compliant wall. The purpose of this compliant wall is to further minimize pressure fluctuations in the ink reservoir during the “start up” of the printhead, until a steady ink flow is established.
However, it has been found that the printed images obtained with an inkjet printer of the type described above may, under certain conditions, still show some undesired artifacts which degrade the image quality.